A fuel cell generates electric power through an electrochemical reaction of an oxidant gas and a fuel gas, and further generates water. Water freezes at or below the freezing point. Thus, when the temperature inside the fuel cell is at or below the freezing point, the product water freezes. Therefore, when the fuel cell is activated in cold areas, etc., it is necessary to prevent the product water from freezing inside the fuel cell until the fuel cell is warmed up.
The below Patent Document 1 discloses a technique of, when the fuel cell is activated under a low temperature, increasing the temperature rise speed of the fuel cell by stopping a cooling water pump when the temperature inside the fuel cell is 0° C. or below and thereby preventing the product water from freezing.